Cummins engines

The X15 is Cummins’ heavy-duty diesel family, with different series and model-year offerings. Cummins distinguishes its Efficiency Series from other X15 configurations and separately describes a 2027 generation. A bare X15 badge does not identify the rating, emissions system or approved application.

The X12 is a Cummins diesel engine family used in truck applications. Cummins’ truck body-builder material lists X12 separately from its larger X15 range. Its published ratings depend on the application and generation, so a fire-apparatus or motorhome rating should not be assumed to apply to a freight truck.

Cummins lists the L9 in its medium-duty truck range. The catalogue contains different model-year entries, including a 2024 medium-duty listing. L9 diesel should be distinguished from L9N natural gas; the similar name does not mean identical fuel, service or vehicle requirements.

The B6.7 is a Cummins medium-duty diesel designation. Cummins publishes truck-specific entries as well as other applications in its product range. Do not assume that a pickup, industrial or other B-series rating describes the commercial truck you are evaluating.

ISX12N is a Cummins natural-gas engine designation. Cummins’ body-builder catalogue includes a 2018 listing, and the company distinguishes it from its later X15N natural-gas offering. It must not be confused with an ISX diesel or treated as a diesel engine with a different fuel-price label.

The L9N is a natural-gas member of Cummins’ truck engine range. It appears separately from the L9 diesel in the manufacturer’s product listings. That fuel distinction affects the vehicle’s supporting systems and the way an operating-cost comparison must be assembled.

Cummins’ X15N is a natural-gas truck engine, distinct from the X15 diesel family. Cummins lists ratings up to 500 hp and 1,850 lb-ft for this offering. These are published family maxima, not a statement that every installed engine has those ratings.